The present invention relates to a composition comprising a stable aqueous dispersion of polymer particles (i.e., a latex) functionalized with structural units of an amino acid such as 6-lysine methacrylate. The composition of the present invention is useful in coating formulations.
Exceptional stain resistance and/or stain blocking of coatings formulated with coatings-grade emulsion polymers is a continuing challenge for formulators, in part because it is often difficult to balance improvements in stain resistance with a concomitant adverse impact on other paint performance properties. To add to the complexity of the problem, an improvement in hydrophobic stain resistance often correlates with a detriment to hydrophilic stain resistance.
For example, it is known that using concentrations of sodium lauryl sulfate surfactant exceeding 2 weight percent can have a positive impact on many hydrophobic stains, but can also compromise water resistance and hydrophilic stain resistance, as well as exacerbate surfactant leeching and water spotting.
Incorporating phosphoethyl methacrylate (PEM) into binders in coatings formulations can greatly improve resistance to hydrophilic stains (coffee, in particular); nevertheless, PEM is known to exacerbate grit formation during the paint making process. Additionally, PEM-containing polymers often exhibit limited compatibility in the presence of certain formulation raw materials (such as certain types of attapulgite or bentonite clays).
Ethyl acrylate (EA) functionalized polymer particles are particularly resistant to lipstick stains, but concentrations of EA exceeding 20% of the total latex particle composition are often required to see this effect, thereby limiting other monomer choices. Moreover, EA has a very low odor threshold, therefore requiring extensive and sometimes costly chasing of residual monomer.
Additionally, many of the acid monomers or adjuncts that are used to achieve colloidal stability, such as surfactants and persulfates, can have a negative impact on stain resistance. Accordingly, it would be an advance in the art of stain resistance to find a way to strike a better balance between stain resistance and other performance properties.